Modulation techniques are commonly employed for transmitting signals in various communication systems. For example, orthogonal frequency division multiplexing (OFDM) has found its way to the high-speed wireless and mobile communication arena. It has been standardized for digital audio broadcast (DAB) in Europe, enabling the mobile reception of high-quality digital audio combined with data services. OFDM has also been adopted for wireless metropolitan and local area networks (WMANs and WLANs) to satisfy the high bit rate requirements of multimedia services and is officially included in the IEEE 802.11 and the IEEE 802.16 (WIMAX) standard.
In an OFDM system, the data is split into N streams, which are independently modulated on parallel closely spaced carrier frequencies or tones. In the applications mentioned above, typically 256 or more tones are used. Practical implementations use an Inverse Fast Fourier Transform (IFFT) to generate a sampled version of the composite time signal. The most distinct advantage of OFDM over single carrier modulation techniques is the easy mitigation of inter-symbol interference and fading, without having to resort to elaborate equalization.
However, high amplitude peaks occur in the composite time signal, when the signals from the different tones add constructively. Compared to the average signal power, the instantaneous power of these peaks is high, and consequently so is the peak to average power ratio. The occurrence of these peaks seriously hampers practical implementations due to for example peak power limitations in the signal processing chain and is generally considered as one of the major drawbacks of the employment of modulation techniques such as OFDM.
There is therefore a need for an improved method of reducing the peak to average power ratio of the composite time signal, for an improved wireless communication system, for a communication network component and for a computer program product comprising computer executable instructions for reducing the peak to average power ratio of the signal.